Series hybrid architectures using compounded doubly fed machines

ABSTRACT

Provided are embodiments of a system including a series hybrid architecture using compounded doubly fed induction machines. Embodiments include a controller configured to control the operation of the system, and a power source configured to convert a first form of energy to a second form of energy. Embodiments also include a first machine configured to generate power, wherein the first machine is mechanically coupled to the power source, and a second machine configured to control equipment, wherein the first machine is electrically coupled to the second machine. Embodiments further include methods for operating the series hybrid architecture using the compounding doubly fed induction machines.

BACKGROUND

The present disclosure relates to power generation systems and moreparticularly to series hybrid architectures using compounded doubly fedinduction machines.

Power generation systems can be based on various sources including thecombustion of fuels including oil, coal, and gas. The power generationsystems can include engines used to produce a force to rotate turbinesthat can be coupled to generators to produce electrical power. Theelectrical power can then be used to power other systems and subsystems.Because the generators are coupled to the engines their electrical powerand frequency is proportional to the rotational speed of the turbine.Techniques for improving the operation of the efficiency of powergeneration are described herein.

BRIEF DESCRIPTION

According to an embodiment, a system including a series hybridarchitecture using compounded doubly fed induction machines is provided.The system includes a controller configured to control the operation ofthe system, and a power source configured to convert a first form ofenergy to a second form of energy. The system also includes a firstmachine configured to generate power, wherein the first machine ismechanically coupled to the power source, and a second machineconfigured to control equipment, wherein the first machine iselectrically coupled to the second machine.

In addition to one or more of the features described herein, or as analternative, further embodiments include a first machine that is adoubly fed induction generator.

In addition to one or more of the features described herein, or as analternative, further embodiments include a second machine that is adoubly fed induction motor.

In addition to one or more of the features described herein, or as analternative, further embodiments include independently operating thefirst machine and the second machine.

In addition to one or more of the features described herein, or as analternative, further embodiments include a first power electronicscircuit that is configured to detect an output of the first machine andprovide a first signal to the first machine to change the output of thefirst machine.

In addition to one or more of the features described herein, or as analternative, further embodiments include a first machine that includes arotor and a stator, where a first signal is provided to the stator ofthe first machine.

In addition to one or more of the features described herein, or as analternative, further embodiments include a second power electronicscircuit that is configured to detect an input to the second machine, andproviding a second signal to control an output of the second machine.

In addition to one or more of the features described herein, or as analternative, further embodiments include a rotor and a stator of asecond machine, where a second signal is provided to the rotor of thesecond machine.

In addition to one or more of the features described herein, or as analternative, further embodiments include a power source that is anengine.

According to another embodiment, a method for operating a series hybridarchitecture using compounded doubly fed induction machines is provided.The method includes generating electrical power at a first machine,transmitting the electrical power to a second machine to operate thesecond machine, and selecting a speed of operation for the secondmachine by controlling the operation of the second machine. The methodalso includes comparing a current speed of operation of the secondmachine to the selected speed of operation, and providing an excitationsignal to the second machine based at least in part on the comparison.

In addition to one or more of the features described herein, or as analternative, further embodiments include modifying the electrical outputof the first machine, wherein modifying the electrical power of thefirst machine includes detecting the electrical power at a first powerelectronics circuit, comparing the electrical power to a value for anelectrical output level, providing an excitation signal to the firstmachine based on the comparison, modifying the electrical power based onthe excitation signal, and providing the modified electrical power tothe second machine.

In addition to one or more of the features described herein, or as analternative, further embodiments include receiving the electrical powerat a second power electronics circuit, comparing the received electricalpower to a value for a threshold level, and providing the excitationsignal to the second machine to control the speed of operation of thesecond machine.

In addition to one or more of the features described herein, or as analternative, further embodiments include a first machine that is adoubly fed induction generator.

In addition to one or more of the features described herein, or as analternative, further embodiments include a second machine that is adoubly fed induction motor.

In addition to one or more of the features described herein, or as analternative, further embodiments include providing the excitation signalto the first machine is provided to rotor windings of the first machine.

In addition to one or more of the features described herein, or as analternative, further embodiments include providing the excitation signalto the second machine is provided to the rotor windings of the secondmachine.

In addition to one or more of the features described herein, or as analternative, further embodiments include a first machine that receivespower to rotate the rotor of the first machine.

In addition to one or more of the features described herein, or as analternative, further embodiments include electrical power that isreceived at a stator of the second machine.

In addition to one or more of the features described herein, or as analternative, further embodiments include receiving energy at the firstmachine from an engine.

In addition to one or more of the features described herein, or as analternative, further embodiments include independently operating thefirst machine and the second machine.

Technical effects of embodiments of the present disclosure includeoperating the gas turbine of the power generation unit at an optimalspeed while independently operating a fan of a vehicle at variousspeeds. In addition, the technical effects also allow for minimizing therequired power electronics used in the system.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation thereof will becomemore apparent in light of the following description and the accompanyingdrawings. It should be understood, however, that the followingdescription and drawings are intended to be illustrative and explanatoryin nature and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 depicts a system for controlling a fan;

FIG. 2 depicts another system for controlling a fan;

FIG. 3 depicts a series hybrid architecture using compounded doubly fedinduction machine in accordance with one or more embodiments;

FIG. 4 depicts a rotor and stator used in a doubly fed induction machinein accordance with one or more embodiments; and

FIG. 5 depicts a flowchart of a method for operating the series hybridarchitecture using compounded doubly fed induction machine in accordancewith one or more embodiments.

DETAILED DESCRIPTION

Induction machines include a stator and rotor which operated to generatea magnetic field to generate an output current. The induction machinescan include generator-type and motor-type machines. The rotor of thegenerator is coupled to a power source that causes the rotor to rotatewithin the magnetic field of the stator to produce an output. A motor isconfigured to receive an electrical input to cause the rotor of themotor to rotate to drive an output such as a fan, pump, or otherequipment.

Doubly fed induction machines can be operated to receive an excitationinput to the stator and rotor to control the output. For example, adoubly fed induction generator can receive an excitation current in therotor windings to change the magnetic field to control the output of thegenerator. Because the output voltage and current are proportional tothe frequency of the rotational speed of the rotor, additional controlcan be achieved by feeding the rotor windings with an excitationcurrent.

A motor, for example, can receive a three-phase electrical input tocause a rotating magnetic field. The excitation current provided to therotor windings can be controlled to modify the rotational speed outputof the motor. In a doubly fed induction motor, the stator and the rotorare used to set the output of the motor. That is, two rotating magneticfields are created and the output is a function of both magnetic fields.The rotational speed of the rotor is now dependent on the speed anddirection of the input to each of the rotating magnetic fields. Byvarying the frequency of the rotor inputs, the speed of the motor can becontrolled.

In existing series hybrid architectures, full rating power electronicsare used to convert power output from the generator. Additional powerelectronics are used to convert the received power to a form that isusable to drive other machines and equipment at a desired operatingspeed. However, the power electronics add significant weight/volume/sizeto the limited area. Power electronics can include large components suchas the capacitors and inductors that can be used in rectifiers, filters,and inverters.

Other existing series hybrid architectures directly link the AC powerfrom the generator to the motor. However, provided in this architecturethe speed of the motor is directly dependent on the speed of thegenerator and the relative generator/motor pole counts. Although thisarchitecture makes use of minimum power electronics, the gas turbinemust be able to run at varying speeds for fan speed control whereindependent fan operation is no longer possible.

The techniques described herein provide for implementing an AC serieshybrid architecture with compounded doubly fed induction machines. Byusing the doubly fed induction machines for the motor and generatorportions of the series hybrid architecture, the motor and generatorspeeds can be decoupled, and the power electronics can be sized to onlyprocess a fraction of the total power thereby minimizing the size of thepower electronics.

Referring to FIG. 1, a system 100 is shown. The system 100 includes anengine 110, which can be coupled to a generator 120. A shaft that iscoupled to a turbine can cause the rotor of the generator 120 to rotatein the magnetic field of the generator 120 to produce electric power.The power from the generator 120 is used to provide power to a motor 130to drive a fan 140. The power from the generator 120 is provided to apower electronics circuit 150 which can convert the AC output of thegenerator to DC. The output of the power electronics circuit 150 can beprovided to a power electronics circuit 160 which produces a controlledAC signal to provide to the motor 130.

However, this particular series configuration requires the full ratedpower electronics circuits 150, 160 which can be very heavy and large.Such elements must be considered when used on vehicles having limitedspace or vehicles used for flight.

Referring now to FIG. 2, another system 200 is shown. The output of thegenerator 220 is directly coupled to the input of a motor 230 that isused to drive the fan 240. The generator 220 outputs an AC signal thatis directly proportional to the operation of the engine 210. Using thisarchitecture, the motor 230 that is used to drive the fan 240 willexperience the variation in the operation of the engine 210 which canlead to inefficient operation.

Now referring to FIG. 3, a system 300 of a series hybrid architectureusing compounded doubly fed induction machines is shown. The engine 310of FIG. 3 can include several components to convert fuel energy tomechanical energy. For example, the engine 310 can be a rotating enginethat receives fuel to produce power to rotate a shaft coupled to thegenerator 320. The engine 310 can include a core, a low/high-pressurecompressor, and a low/high-pressure turbine (not shown) to convert thefuel energy to rotational energy for the generator 320.

In one embodiment, the first machine 320 is a doubly fed inductiongenerator. The rotor of the doubly fed induction generator is controlledby the rotation of the turbine of the engine which causes the rotor torotate in the magnetic field producing current. The doubly fed inductiongenerator can receive an excitation current to rotor windings (notshown) which can modify the electrical power output of the generator.The doubly fed induction generator can also receive an excitationcurrent at the stator where the electrical output of the generator is afunction of both the magnetic field of the stator and rotor.

In some embodiment, the second machine 330 is a doubly fed inductionmotor. The doubly fed induction motor is configured to receive a firstinput such as the electrical output from the generator. The receivedinput can be a 3-phase AC input and can be provided to the stator togenerate a magnetic field in the motor. The input is provided to thestator which in turns drives the rotor. The doubly fed induction motorcan also receive an excitation signal to the rotor to modify therotational output of the motor. That is, the rotational speed of theshaft of the motor which can be used to drive the fan can be changed andcontrolled at a desired operational speed using the excitation signal.

A first power/frequency converter 350 can monitor the output of thegenerator 320. The output of the power/frequency converter 350 can beadjusted to control the output electrical power of the generator 320 asdesired. That is, the output of the stator can be modified by the signalfrom the power/frequency converter 350 provided to the rotor windings toeffect the electrical power output the generator 320. For example, theconverter 350 can detect the AC power and compare it to a thresholdlevel. Based on the comparison the excitation signal can be provided tothe rotor of the generator 320 to change the magnetic field whichaffects the electrical output of the generator 320.

A second power/frequency converter 360 can monitor an electrical inputto the motor 330. The converter 360 can compare the input to a thresholdlevel. Based on the comparison the excitation signal can be provided tothe rotor of the motor 330 to change the magnetic field which affectsthe rotational speed of the motor 330.

A controller 370 can be used to control the operation of the first andsecond power/frequency converter. By implementing a doubly fed inductiongenerator and doubly fed induction motor in a series hybridarchitecture, the power electronics can be sized and reduced. Inaddition, the engine 310 can be operated at a reduced optimal speedwhile providing flexible control an electric motor coupled to agenerator. By using the doubly fed induction machines the engine can beoperated at a reduced rate or an optimal rate and the fan speed can nowbe independently controlled.

Referring now to FIG. 4, a doubly fed induction machine 400 (hereinafterreferred to as “machine 400”) in accordance with one or more embodimentsis shown. The machine 400 includes a stator 410 and a rotor 420 toproduce mechanical force when operating as a motor and produceelectrical power when operating as a generator. In one or moreembodiments the stator 410 is configured to receive excitation signal430 to energize the stator 410. The excitation signal 430 can include anAC or DC signal. The rotor 420 can receive an excitation signal 440 tomodify the output of the machine 400. When operating as a generator, theelectrical output of the machine can be a function of both excitationsignals 430, 440. When operating as a motor, the rotational speed of therotor 440 of the machine 400 can be a function of both excitationsignals 430, 440. The excitation signals 430, 440 can be provided towindings that are in the rotor 420 or coils in the stator 410. In someembodiments, the excitation signals 430, 440 can be controlled by systemcontrollers and power/frequency converters such as that shown in FIG. 3.

Now referring to FIG. 5, a method 500 for controlling a series hybridarchitecture using compounded doubly fed induction machines is shown.The method 500 can be implemented in the series hybrid architecture suchas that shown in FIG. 3. It should be understood the method 500 can alsobe implemented in architectures having a different configuration and isnot limited to that shown in FIG. 3. The method 500 begins at block 502and proceeds to block 504 which provides for generating electrical powerat a first machine. The electrical power can be generated by a generatorsuch as a doubly fed induction generator.

The method 500 at block 506 provides for transmitting the electricalpower to a second machine to operate the second machine. In one or moreembodiments, the second machine is a doubly fed induction motor. Themotor can receive the electrical power at a stator of the motor whichcauses the rotor to rotate at a speed which can be used to driveequipment such as a fan.

Block 508 provides for selecting a speed of operation for the secondmachine. The speed can be selected to operate a fan at a desired speed.The motor speed is not completely dependent on the electrical power fromthe generator.

At block 510, the method 500 provides for comparing a current speed ofoperation of the second machine to the selected speed of operation.Continuing to block 512 the method 500 includes providing an excitationsignal to the second machine based at least in part on the comparison.The excitation signal can be an AC excitation signal that is provided tothe rotor where the speed of the rotor will be a function of thereceived AC power from the generator and the received AC excitationsignal received at the rotor of the motor. The method 500 ends at block514. It is to be understood that one or more steps can be continuouslyrepeated. In addition, other steps and or a different combination ofsteps can be used.

The technical effects and benefits provide an architecture that will usea fraction of the power electronics for minimum weight, volume, andlosses while maintaining maximum fan speed control. This architectureallows for innovative vehicle architectures and failure mode operation.The technical effects and benefits include a reduction in the size ofthe power electronics. Since the power electronics are now only requiredto process a fraction of the total power, they can be sized accordinglyto reduce its weight, volume, and size.

The technical effects and benefits allow for the operation of the engineat a reduced speed while maintaining the desired performance at acoupled device such as a motor driving a fan or pump.

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

As described above, embodiments can be in the form ofprocessor-implemented processes and devices for practicing thoseprocesses, such as a processor. Embodiments can also be in the form ofcomputer program code containing instructions embodied in tangiblemedia, such as network cloud storage, SD cards, flash drives, floppydiskettes, CD ROMs, hard drives, or any other computer-readable storagemedium, wherein, when the computer program code is loaded into andexecuted by a computer, the computer becomes a device for practicing theembodiments. Embodiments can also be in the form of computer programcode, for example, whether stored in a storage medium, loaded intoand/or executed by a computer, or transmitted over some transmissionmedium, loaded into and/or executed by a computer, or transmitted oversome transmission medium, such as over electrical wiring or cabling,through fiber optics, or via electromagnetic radiation, wherein, whenthe computer program code is loaded into an executed by a computer, thecomputer becomes an device for practicing the embodiments. Whenimplemented on a general-purpose microprocessor, the computer programcode segments configure the microprocessor to create specific logiccircuits.

The term “about” is intended to include the degree of error associatedwith measurement of the particular quantity based upon the equipmentavailable at the time of filing the application.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,element components, and/or groups thereof.

While the present disclosure has been described with reference to anexemplary embodiment or embodiments, it will be understood by thoseskilled in the art that various changes may be made and equivalents maybe substituted for elements thereof without departing from the scope ofthe present disclosure. In addition, many modifications may be made toadapt a particular situation or material to the teachings of the presentdisclosure without departing from the essential scope thereof.Therefore, it is intended that the present disclosure not be limited tothe particular embodiment disclosed as the best mode contemplated forcarrying out this present disclosure, but that the present disclosurewill include all embodiments falling within the scope of the claims.

What is claimed is:
 1. A method for operating a series hybridarchitecture using compounded doubly fed induction machines, the methodcomprising: generating electrical power at a first machine; transmittingthe electrical power to a second machine to operate the second machine;selecting a speed of operation for the second machine by controlling theoperation of the second machine; comparing a current speed of operationof the second machine to the selected speed of operation; and providingan excitation signal to the second machine based at least in part on thecomparison, wherein the first machine and the second machine areindependently operated; further comprising modifying the electricaloutput of the first machine, wherein modifying the electrical power ofthe first machine comprises: detecting the electrical power at a firstpower electronics circuit; comparing the electrical power to a value foran electrical output level; providing an excitation signal to the firstmachine based on the comparison; further comprising receiving theelectrical power at a second power electronics circuit; comparing thereceived electrical power to a value for a threshold level; andproviding the excitation signal to the second machine to control thespeed of operation of the second machine, wherein the first powerelectronics circuit is not connected to the second power electronicscircuit over a direct current (DC) link.
 2. The method of claim 1,further comprising modifying the electrical output of the first machine,wherein modifying the electrical power of the first machine comprises:modifying the electrical power based on the excitation signal; andproviding the modified electrical power to the second machine.
 3. Themethod of claim 1, wherein the first machine is a doubly fed inductiongenerator.
 4. The method of claim 3, wherein the second machine is adoubly fed induction motor.
 5. The method of claim 1, wherein providingthe excitation signal to the first machine is provided to rotor windingsof the first machine.
 6. The method of claim 1, wherein providing theexcitation signal to the second machine is provided to the rotorwindings of the second machine.
 7. The method of claim 1, furthercomprising receiving power at the rotor of the first machine.
 8. Themethod of claim 1, further comprising receiving the electrical power ata stator of the second machine.
 9. The method of claim 1, furthercomprising receiving energy at the first machine from an engine.